This invention relates to a multicylinder rotary compressor for use in an air conditioner, a refrigerator, or the like. More particularly, it relates to a multicylinder rotary compressor in which capacity control can be performed by unloading one of the cylinders of the compressor.
In a cooling system such as an air conditioner or refrigerator, it is often necessary to adjust the capacity of the compressor of the cooling system in accordance with the load. The conventional method of capacity control is by turning the compressor motor on and off in response to some parameter such as the temperature in the space being cooled. However, if the cooling system employs only a single compressor, this method allows only very coarse adjustment of the capacity.
For a multicylinder rotary compressor having a plurality of cylinders which are driven by a single crankshaft, more refined capacity control can be performed by selectively stopping one or more of the cylinders of the compressor. In one form of rotary compressor, the crankshaft consists of a plurality of sections, each of which drives a different cylinder. The sections of the crankshaft are connected together by clutches, and by selectively engaging the clutches, a varying number of cylinders can be driven by the crankshaft, thereby varying the capacity of the compressor. However, a rotary compressor of this type has a more complicated structure than one with a one-piece crankshaft, which makes it more expensive to manufacture and less reliable.
A recently-proposed method of capacity control for a multicylinder rotary compressor with a one-piece crankshaft is the suction line cut-off method in which the suction line of one of the cylinders of the compressor is completely blocked. The pressure within the cylinder is reduced to substantially a vacuum, so that the cylinder is unloaded and the output thereof falls to zero.